1. Field of the Invention
The present disclosure relates to an apparatus for measuring the position and shape of a pattern that is formed on, for example, a sheet-shaped base material by coating or printing.
2. Description of the Related Art
In processes of manufacturing, for example, electrodes for capacitors or batteries, materials (coating substances) that realize specific electrical properties are applied to sheet base materials (simply referred to as sheets hereinafter). In this case, the coating substance is sometimes applied over the entire surface of a sheet. However, when the coating substance is expensive or the edge surfaces of the sheet need be free of the coating substance, only specified portions of the sheet are coated.
Such coating is referred to as partial coating, block coating, pattern coating, or the like.
To perform such coating, dimensions (width and length) of portions to be subject to coating are measured. When both surfaces of the sheet are to be coated, dimensional offsets (width and length) of the coating portions between the top and bottom surfaces also need be measured and controlled.
FIG. 6 is a conceptual diagram illustrating an example of a related-art coating pattern measuring apparatus using cameras for measurement. In FIG. 6, the sheet 1 is supported by transport rollers (not shown) and transported on a coating line at a constant speed. A plurality of cameras 31 (two cameras 31 in FIG. 6), to which lenses 30 are attached, are disposed on the coating line so as to measure coating dimensions.
In order to measure dimensions on the sheet 1, since the sheet moves at a constant speed, the cameras 31 need not have two-dimensional information. For this reason, line sensor cameras are widely used. In the line sensor camera, sensors as image pickup elements are arranged along a line perpendicular to a sheet moving direction. It is clear that an area sensor camera, which has two-dimensional information in image pickup elements, may instead be used. The sheet 1 includes coating portions 32 and portions to be observed 33.
For such a coating dimension measuring system, the following capabilities are required:
1. Resistance to Effects from Pass Line Variation
The sheet 1 is ideally transported at the same position on a transport line. In this case, the position where the sheet 1 passes through is referred to as a pass line. However, the sheet 1 does not actually pass through the completely same position in part of the coating line, but passes through vertically or laterally varied positions. For example, in a portion between the transport rollers and the like, where any support is not provided, the sheet 1 may vertically vibrate (a pass line variation). It is highly desirable that measurement of coating dimensions is free of that positional variation.
2. Flexible Accommodation of Coating Patterns
In FIG. 6, the sheet 1 has one coating pattern in a width direction thereof (single-row coating). Alternatively, a plurality of coating patterns may be formed in the sheet width direction. For example, two coating patterns may be formed in the sheet width direction (double-row coating). In this case, three cameras are required for picking up images.
Furthermore, three or four rows of coating patterns may be arranged in the width direction. For such cases, it is desirable that image pickup can be performed over the entire width of the sheet 1.
3. Size Reduction
Since the size of the coating line directly affects production costs, the size of the coating line is desirably reduced as much as possible.
Japanese Unexamined Patent Application Publications No. 2002-42789 and No. 2004-148534 are examples of related art.